I figured I should more properly illustrate the differences between Nicky and his alter-ego/future-self in one image! So here we have Nicky at 10 and his late teens when he starts going by Sonic.
In this AU, Sonic's eyes are not naturally green! He's always had vision problems, and used to wear glasses. But he switched to contacts once he learned how to zip around at supersonic speeds. He trades in the sweater for a scarf, and goes for fingerless gloves for that 'cool' factor. While as a child, he would put things in his ankle bags, he since learned how to store things in his quills, eliminating the need for extra gear.
Oh, and after a few years, he realized he much preferred guys over girls, which the time travel shenanigans influences that to happen a bit faster, leading him to go from his girlfriend Amy to his dad Paulie. He also likes chubby guys, which only adds to his lust for the big mailman.